It is known to utilise laser light for tissue treatment.
During tissue treatment, a laser ablates a thin epidermal layer of the derma of a patient. During healing, a new epidermal layer is formed on the ablated surface having the look of the derma of a young person, i.e. the new epidermal layer is formed without previously existing scars, wrinkles, etc.
Lasers that operate at a wavelength that is absorbed in water are used for tissue treatment. When the laser power density (W/mm2) at illuminated cells is sufficient, cellular water is superheated causing small explosions that disrupt heated cells.
During removal of an epidermal layer, it is essential not to damage underlying or surrounding tissue. Residual heat may cause non-ablated cells to char and become necrotic, whereby new scars may be formed and thus, it is desirable to apply laser power for a short time, to minimize transmission of conducted heat to underlying and surrounding tissue.
It is therefore desired to accurately control the amount of light energy transferred to derma to be ablated. The amount of energy must be sufficient for the dermal cells to vaporize and, simultaneously, the amount of residual energy heating non-ablated cells must be so low that non-ablated cells will not be damaged.
Apparatuses for tissue treatment are known, comprising a CO2 laser emitting a laser beam and a laser articulating arm with mirrors for reflection of the laser beam, so that the laser beam is transmitted inside the articulating arm. Further, the arm has a number of joints, so that the arm can be moved around by an operator. A handpiece to be held by the operator is connected to the arm. The laser beam is moved or scanned across a target surface by movable mirrors connected to motors and mounted in the arm. The scan pattern of the laser beam is an archimedes spiral. The laser spot formed by the laser beam on the target surface moves along the spiral at a constant angular speed.
It is a disadvantage of the known apparatus that the energy density delivered to the target surface is non-uniform across the scanned surface area of the spiral, as more energy is delivered at the centre of the spiral than at the circumferential of the spiral.
It is another disadvantage of the known apparatus that the circular outline of the scan pattern leads to non-uniform scanning of an area that is larger than the area of the scan spiral as either 1) areas that have not been scanned will remain on the surface, when abutting spirals or 2) ablated areas will be scanned more than once, due to overlap of spirals.
It is yet another disadvantage of the known apparatus that evaporated derma is exhausted through the internal of the laser articulation arm, whereby optics and other members in the arm get dirty.
It is still another disadvantage of the known apparatus that it is very laborious to disassemble members, that may have been in contact with a patient, from the handpiece, e.g., for autoclaving.
It is still another disadvantage of the known apparatus that movement of the handpiece is restrained by the laser articulation arm, as the construction of tubes interconnected by joints is not fully flexible.
In addition, these apparatus typically have large mass and a large inertia (typically also due to counter-balancing masses) which makes the operation and movement of the arm difficult and heavy.
Under the name Uni-laser 450P, Asah Medico A/S, Denmark, markets an apparatus for cosmetic tissue treatment, comprising a CO2 laser and an optical fiber coupled to the laser at one end and to a handpiece at the other end.
It is a disadvantage of this known apparatus that the laser beam is manually scanned across the target surface whereby the quality of the treatment is determined and limited by the skill of the operator.